Los Angeles Mayor Eric Garcetti says the union-backed contract proposal would limit Department of Water and Power reforms. But he may face an uphill battle.

Los Angeles Mayor Eric Garcetti on Thursday set the stage for a potentially messy confrontation with the City Council, saying he would refuse to sign a proposed salary deal with the politically potent union representing Department of Water and Power workers.

Local 18 of the International Brotherhood of Electrical Workers ran a fierce campaign against Garcetti, whose main argument in the mayoral election in May was that he could be trusted to stand up for DWP ratepayers.

In a written statement, Garcetti said the union-endorsed contract proposal included cost savings that were worth pursuing. But he said he could not approve it "because it limits further DWP reforms, specifically to the department's costly and inefficient work rules."

"The voters of Los Angeles have been clear — they want fundamental DWP reform and so do I," Garcetti said.

But what the utility workers can't get from the mayor, they could well get from the City Council. The council's leaders have put the proposed four-year DWP labor pact on track for approval by Sept. 1, starting with a public hearing Friday.

City policy analysts have embraced the deal, highlighting its promise of three years without pay hikes; the postponement of a required October raise until 2016; and reduced pension benefits and a higher retirement age for new hires.

This is the first major union deal on Garcetti's watch. His isolation on the issue — he is the only elected official to publicly question the proposal's merits — underscores labor's influence at City Hall, even after a campaign in which unions tilted heavily against Garcetti.

The momentum behind the proposed labor pact is drawing renewed attention to the millions of dollars the DWP union has poured into city elections. The IBEW spent $2 million on its fight against Garcetti and has shown a willingness to spend six-figure sums on independent campaigns to elect council members.

In 2011, political groups controlled by IBEW leaders put more than $614,000 into a campaign to unseat an adversary, Councilman Bernard C. Parks, and nearly $528,000 to elect a new Harbor-area council member — including just over $188,000 on the ultimate winner, Joe Buscaino. This year, IBEW affiliates donated $75,000 to the council's failed ballot measure to increase the city's sales tax.

Whether Garcetti can persuade the council to back him in seeking more concessions is far from clear. Councilman Paul Koretz, who backed Garcetti for mayor, said he was leaning toward approval of the proposed labor deal, calling it "one of the better contracts we've had historically" at the utility.

"There are folks that think we could make it better," said Koretz, who won his office in 2009 with nearly $40,000 in support from IBEW affiliates. "I'm inclined to think there's mostly downsides to continuing [negotiations] and not much upside."

For Garcetti, the political dimensions of the deal are hard to escape. The union's advertising campaign during the mayor's race portrayed him as a leader who had indulged in luxury travel at public expense and whose mismanagement had driven the city to the brink of bankruptcy.

For weeks, Garcetti insisted the proposed pact didn't go far enough in holding down costs at the DWP as it prepared to impose the next in a series of water and power rate hikes in the months ahead.

As council approval appeared more likely, Garcetti changed his tone and began to praise some of the deal's cost-cutting features. He credited "the strength of the message" of his campaign.

"Nobody questions that this election changed the game," he said, recalling his frequent pledge to be independent of the DWP union. "This was unimaginable five months ago."

But his announcement on the eve of the council's hearing raised the specter of a veto and the political drama of a council override. The council and union could adjust the deal to suit Garcetti, but that that would require accommodations from Brian D'Arcy, the savvy DWP union leader.

D'Arcy did not comment on Garcetti's opposition to the deal, saying instead that he was looking forward to Friday's hearing — and a discussion of "the significant reforms that have been negotiated and previously agreed to by the city.

"This agreement will save billions of dollars, create pension sustainability, and affordable rates for DWP customers for the foreseeable future," he said in a prepared statement.

The union's current contract doesn't expire until the fall of 2014, but council leaders say they must act fast to stop an already approved Oct. 1 raise.

A spokesman said Council President Herb Wesson was searching for common ground between Garcetti and the DWP union. "What he wants to do right now is keep the discussions and the conversations going," Wesson aide Ed Johnson said.